Marine engine lubrication

ABSTRACT

Trunk piston marine engine lubrication, when the engine is fueled by heavy fuel oil, is effected by a composition of TBN in the range of 20 to 60 comprising a major amount of an oil of lubricating viscosity containing 50 mass % or more of a Group 1 basestock, and respective minor amounts of an overbased metal calcium alkyl salicylate detergent providing 40 to 90 mmol of calcium alkyl salicylate per kg of the composition, and 0.1 to 10 mass %, based on the mass of the composition, of an oil-soluble linear alkyl-substituted phenol. Asphaltene precipitation in the lubricant, caused by the presence of contaminant heavy fuel oil, is prevented or inhibited.

FIELD OF THE INVENTION

This invention relates to a trunk piston marine engine lubricatingcomposition for a medium-speed four-stroke compression-ignited (diesel)marine engine and lubrication of such an engine.

BACKGROUND OF THE INVENTION

Marine trunk piston engines generally use Heavy Fuel Oil (‘HFO’) foroffshore running. Heavy Fuel Oil is the heaviest fraction of petroleumdistillate and comprises a complex mixture of molecules including up to15% of asphaltenes, defined as the fraction of petroleum distillate thatis insoluble in an excess of aliphatic hydrocarbon (e.g. heptane) butwhich is soluble in aromatic solvents (e.g. toluene). Asphaltenes canenter the engine lubricant as contaminants either via the cylinder orthe fuel pumps and injectors, and asphaltene precipitation can thenoccur, manifested in ‘black paint’ or ‘black sludge’ in the engine. Thepresence of such carbonaceous deposits on a piston surface can act as aninsulating layer which can result in the formation of cracks that thenpropagate through the piston. If a crack travels through the piston, hotcombustion gases can enter the crankcase, possibly resulting in acrankcase explosion.

It is therefore highly desirable that trunk piston engine oils (‘TPEO’s)prevent or inhibit asphaltene precipitation. The prior art describesways of doing this.

WO 96/26995 ('995) discloses the use of a hydrocarbyl-substituted phenolto reduce ‘black paint’ in a diesel engine. Specifically, it mentions alubricating oil for lubricating a medium-speed 4-stroke diesel engine,such oils also being known in the art as TPEO's. It mentions use ofalkyl phenols to reduce black paint formation in use of such oils withfuel oils with a residual oil content, also known in the art as HFO's.'995 further mentions that the lubricating oil may contain detergentssuch as hydrocarbyl-substituted alkaline earth metal phenates,salicylates, napththenates, sulphonates or carboxylates, which may benormal or overbased.

'995 also mentions that the lubricating oil has a TBN of 8-50, providedby adjusting the amount of detergent, for use in a 4-stroke engine, and0.5 to 10% by weight of the phenol. Its examples describe sedimentstests on TPEO's of 30 TBN containing a calcium phenate detergent andeither no or varying amounts of a branched chain alkyl phenol.

'995 is not, however, concerned with the economics of treating TPEO's toinhibit ‘black paint’ formation. A considerable cost arises from theamount of detergent soap that is used, i.e. the detergent other than thebasic material. It is now found that, when the detergent is asalicylate, there is a relationship between ‘black paint’ reducingperformance and the respective concentrations of salicylate soap and ofalkyl phenol. This relationship is such that the level of soap may bereduced, and cost reduced, without any deleterious effect on ‘blackpaint’ reducing performance.

WO 2010/124859 describes trunk piston marine engine lubrication where,to prevent or inhibit asphaltene precipitation, the lubricant comprisesa Group II basestock and respective minor amounts of an overbased metalsalicylate detergent and an alkyl-substituted phenol, other than ahindered phenol.

SUMMARY OF THE INVENTION

The following are now found when a salicylate detergent/alkyl phenolsystem is used in TPEO's in attempting to reduce or eliminate ‘blackpaint’. When the salicylate soap concentration is high, addition ofalkyl phenol does not substantially affect performance. However, whenthe salicylate soap level is lower, additions of low levels of alkylphenol, for example below those stated in '995 to be preferred (i.e.2.0% by weight) and even below those stated generally in '995 (i.e. 0.5%by weight), are found to improve performance.

A first aspect of the invention is a trunk piston marine enginelubricating oil composition of TBN in the range of 20 to 60, such as, 30to 55, for improving asphaltene handling in use thereof, in operation ofthe engine when fuelled by a heavy fuel oil, which composition comprisesor is made by admixing an oil of lubricating viscosity, in a majoramount, containing 50 mass % or more of a Group 1 basestock, and, inrespective minor amounts:

-   -   (A) an overbased calcium alkyl salicylate detergent providing 40        to 90, such as, 50 to 85, mmol of calcium alkyl salicylate per        kg of the composition, as determined by titration; and    -   (B) 0.1 to 10, such as 0.1 to less than 2.0, for example to 1.5,        mass % active ingredient, based on the mass of the composition,        of an oil-soluble linear (straight chain) alkyl-substituted        phenol.

A second aspect of the invention is the use of a detergent (A) incombination with a component (B) as defined in, and in the amountsstated in, the first aspect of the invention in a trunk piston marinelubricating oil composition of TBN in the range of 20 to 60, such as, 30to 55, for a medium-speed compression-ignited marine engine, whichcomposition comprises an oil of lubricating viscosity in a major amountand contains 50 mass % or more of a Group 1 basestock, to improveasphaltene handling during operation of the engine, fueled by a heavyfuel oil and its lubrication by the composition.

A third aspect of the invention is a method of operating a trunk pistonmedium-speed compression-ignited marine engine comprising

-   -   (i) fueling the engine with a heavy fuel oil; and    -   (ii) lubricating the crankcase of the engine with a composition        as defined in the first aspect of the invention.

A fourth aspect of the invention is a method of dispersing asphaltenesin a trunk piston marine lubricating oil composition during itslubrication of surfaces of the combustion chamber of a medium-speedcompression-ignited marine engine and operation of the engine, whichmethod comprises

-   -   (i) providing a composition as defined in the first aspect of        the invention;    -   (ii) providing the composition in the combustion chamber;    -   (iii) providing heavy fuel oil in the combustion chamber; and    -   (iv) combusting the heavy fuel oil in the combustion chamber.

In this specification, the following words and expressions, if and whenused, have the meanings ascribed below:

-   -   “active ingredients” or “(a.i.)” refers to additive material        that is not diluent or solvent;    -   “comprising” or any cognate word specifies the presence of        stated features, steps, or integers or components, but does not        preclude the presence or addition of one or more other features,        steps, integers, components or groups thereof; the expressions        “consists of” or “consists essentially of” or cognates may be        embraced within “comprises” or cognates, wherein “consists        essentially of” permits inclusion of substances not materially        affecting the characteristics of the composition to which it        applies;    -   “major amount” means 50 mass % or more of a composition;    -   “minor amount” means less than 50 mass % of a composition;    -   “TBN” means total base number as measured by ASTM D2896.

Furthermore in this specification, if and when used:

-   -   “calcium content” is as measured by ASTM 4951;    -   “phosphorus content” is as measured by ASTM D5185;    -   “sulphated ash content” is as measured by ASTM D874;    -   “sulphur content” is as measured by ASTM D2622;    -   “KV100” means kinematic viscosity at 100° C. as measured by ASTM        D445.

Also, it will be understood that various components used, essential aswell as optimal and customary, may react under conditions offormulation, storage or use and that the invention also provides theproduct obtainable or obtained as a result of any such reaction.

Further, it is understood that any upper and lower quantity, range andratio limits set forth herein may be independently combined.

DETAILED DESCRIPTION OF THE INVENTION

The features of the invention will now be discussed in more detailbelow.

Oil of Lubricating Viscosity

The lubricating oils may range in viscosity from light distillatemineral oils to heavy lubricating oils. Generally, the viscosity of theoil ranges from 2 to 40 mm²/sec, as measured at 100° C.

Natural oils include animal oils and vegetable oils (e.g., castor oil,lard oil); liquid petroleum oils and hydrorefined, solvent-treated oracid-treated mineral oils of the paraffinic, naphthenic and mixedparaffinic-naphthenic types. Oils of lubricating viscosity derived fromcoal or shale also serve as useful base oils.

Synthetic lubricating oils include hydrocarbon oils and halo-substitutedhydrocarbon oils such as polymerized and interpolymerized olefins (e.g.,polybutylenes, polypropylenes, propylene-isobutylene copolymers,chlorinated polybutylenes, poly(1-hexenes), poly(1-octenes),poly(1-decenes)); alkybenzenes (e.g., dodecylbenzenes,tetradecylbenzenes, dinonylbenzenes, di(2-ethylhexyl)benzenes);polyphenyls (e.g., biphenyls, terphenyls, alkylated polyphenols); andalkylated diphenyl ethers and alkylated diphenyl sulphides andderivative, analogues and homologues thereof.

Alkylene oxide polymers and interpolymers and derivatives thereof wherethe terminal hydroxyl groups have been modified by esterification,etherification, etc., constitute another class of known syntheticlubricating oils. These are exemplified by polyoxyalkylene polymersprepared by polymerization of ethylene oxide or propylene oxide, and thealkyl and aryl ethers of polyoxyalkylene polymers (e.g.,methyl-polyiso-propylene glycol ether having a molecular weight of 1000or diphenyl ether of poly-ethylene glycol having a molecular weight of1000 to 1500); and mono- and polycarboxylic esters thereof, for example,the acetic acid esters, mixed C₃-C₈ fatty acid esters and C₁₃ oxo aciddiester of tetraethylene glycol.

Another suitable class of synthetic lubricating oils comprises theesters of dicarboxylic acids (e.g., phthalic acid, succinic acid, alkylsuccinic acids and alkenyl succinic acids, maleic acid, azelaic acid,suberic acid, sebacic acid, fumaric acid, adipic acid, linoleic aciddimer, malonic acid, alkylmalonic acids, alkenyl malonic acids) with avariety of alcohols (e.g., butyl alcohol, hexyl alcohol, dodecylalcohol, 2-ethylhexyl alcohol, ethylene glycol, diethylene glycolmonoether, propylene glycol). Specific examples of such esters includesdibutyl adipate, di(2-ethylhexyl)sebacate, di-n-hexyl fumarate, dioctylsebacate, diisooctyl azelate, diisodecyl azelate, dioctyl phthalate,didecyl phthalate, dieicosyl sebacate, the 2-ethylhexyl diester oflinoleic acid dimer, and the complex ester formed by reacting one moleof sebacic acid with two moles of tetraethylene glycol and two moles of2-ethylhexanoic acid.

Esters useful as synthetic oils also include those made from C₅ to C₁₂monocarboxylic acids and polyols and polyol esters such as neopentylglycol, trimethylolpropane, pentaerythritol, dipentaerythritol andtripentaerythritol.

Silicon-based oils such as the polyalkyl-, polyaryl-, polyalkoxy- orpolyaryloxysilicone oils and silicate oils comprise another useful classof synthetic lubricants; such oils include tetraethyl silicate,tetraisopropyl silicate, tetra-(2-ethylhexyl)silicate,tetra-(4-methyl-2-ethylhexyl)silicate,tetra-(p-tert-butyl-phenyl)silicate,hexa-(4-methyl-2-ethylhexyl)disiloxane, poly(methyl)siloxanes andpoly(methylphenyl)siloxanes. Other synthetic lubricating oils includeliquid esters of phosphorus-containing acids (e.g., tricresyl phosphate,trioctyl phosphate, diethyl ester of decylphosphonic acid) and polymerictetrahydrofurans.

Unrefined, refined and re-refined oils can be used in lubricants of thepresent invention. Unrefined oils are those obtained directly from anatural or synthetic source without further purification treatment. Forexample, a shale oil obtained directly from retorting operations;petroleum oil obtained directly from distillation; or ester oil obtaineddirectly from esterification and used without further treatment, areunrefined oils. Refined oils are similar to unrefined oils except thatthe oil is further treated in one or more purification steps to improveone or more properties. Many such purification techniques, such asdistillation, solvent extraction, acid or base extraction, filtrationand percolation, are known to those skilled in the art. Re-refined oilsare obtained by processes similar to those used to provide refined oilsbut begin with oil that has already been used in service. Suchre-refined oils are also known as reclaimed or reprocessed oils and areoften subjected to additional processing using techniques for removingspent additives and oil breakdown products.

The American Petroleum Institute (API) publication “Engine Oil Licensingand Certification System”, Industry Services Department, FourteenthEdition, December 1996, Addendum 1, December 1998 categorizes Group 1base stocks as follows:

Group I base stocks contain less than 90 percent saturates and/orgreater than 0.03 percent sulphur and have a viscosity index greaterthan or equal to 80 and less than 120 using the test methods specifiedin Table E-1.

Analytical Methods for Base Stock are tabulated below:

PROPERTY TEST METHOD Saturates ASTM D 2007 Viscosity Index ASTM D 2270Sulphur ASTM D 2622 ASTM D 4294 ASTM D 4927 ASTM D 3120

As stated, the oil of lubricating viscosity in this invention contains50 mass % or more of the defined basestock or a mixture thereof.Preferably, it contains 60, such as 70, 80 or 90, mass % or more of thedefined basestock or a mixture thereof. The oil of lubricating viscositymay be substantially all the defined basestock or a mixture thereof.

Overbased Calcium Alkyl Salicylate Detergent (A)

A metal detergent is an additive based on so-called metal “soaps”, thatis metal salts of acidic organic compounds, sometimes referred to assurfactants. They generally comprise a polar head with a longhydrophobic tail. Overbased metal detergents, which comprise neutralizedmetal detergents as the outer layer of a metal base (e.g. carbonate)micelle, may be provided by including large amounts of metal base byreacting an excess of a metal base, such as an oxide or hydroxide, withan acidic gas such as carbon dioxide.

In the present invention, (A) are overbased calcium alkyl-substitutedsalicylates.

The overbased detergent typically has the structure shown:

wherein R is a linear alkyl group. There may be more than one R groupattached to the benzene ring. The COO⁻ group can be in the ortho, metaor para position with respect to the hydroxyl group; the ortho positionis preferred. The R group can be in the ortho, meta or para positionwith respect to the hydroxyl group.

Salicylic acids are typically prepared by the carboxylation, by theKolbe-Schmitt process, of phenoxides, and in that case, will generallybe obtained (normally in a diluent) in admixture with uncarboxylatedphenol. Salicylic acids may be non-sulphurized or sulphurized, and maybe chemically modified and/or contain additional substituents. Processesfor sulphurizing an alkyl salicylic acid are well known to those skilledin the art, and are described, for example, in US 2007/0027057.

The alkyl groups advantageously contain 5 to 100, preferably 9 to 30,especially 14 to 24, carbon atoms.

The term “overbased” is generally used to describe metal detergents inwhich the ratio of the number of equivalents of the metal moiety to thenumber of equivalents of the acid moiety is greater than one. The term‘low-based’ is used to describe metal detergents in which the equivalentratio of metal moiety to acid moiety is greater than 1, and up to about2.

By an “overbased calcium salt of surfactants” is meant an overbaseddetergent in which the metal cations of the oil-insoluble metal salt areessentially calcium cations. Small amounts of other cations may bepresent in the oil-insoluble metal salt, but typically at least 80, moretypically at least 90, for example at least 95, mole %, of the cationsin the oil-insoluble metal salt, are calcium ions. Cations other thancalcium may be derived, for example, from the use in the manufacture ofthe overbased detergent of a surfactant salt in which the cation is ametal other than calcium. Preferably, the metal salt of the surfactantis also calcium.

Carbonated overbased metal detergents typically comprise amorphousnanoparticles. Additionally, there are disclosures of nanoparticulatematerials comprising carbonate in the crystalline calcite and vateriteforms.

The basicity of the detergents may be expressed as a total base number(TBN). A total base number is the amount of acid needed to neutralizeall of the basicity of the overbased material. The TBN may be measuredusing ASTM standard 1)2896 or an equivalent procedure. The detergent mayhave a low TBN (i.e. a TBN of less than 50), a medium TBN (i.e. a TBN of50 to 150) or a high TBN (i.e. a TBN of greater than 150, such as150-500).

As stated, 40-90, such as, 50-85, mmol of calcium alkyl salicylate perkg of the composition is provided, the values being determined bytitration. Preferably, the values are in the range of 50-80, morepreferably 50-70, mmol/kg.

Linear Alkyl-Substituted Phenol (B)

As stated, the phenol constitutes 0.1 to 10, preferably 0.1 to less than2.0, such as 0.1 to 1.5, mass % of the mass of the composition. Also, itmay constitute from 0.1 or from 0.25 to less than 0.5, mass % of themass of the composition. It may be present in the range of 0.2 or 0.25to 5 or 10 mass %.

The alkyl substitution in (B) may be mono, for example by way of astraight chain alkyl group having from 9 to 30, preferably 14 to 24,carbon atoms.

As an example of alkylphenol (B) there may be mentioned an alkylbenzenol where the alkyl substitution is, for example, in the 2-positionor in the 4-position.

(A) and (B) may be provided for the purpose of the invention by blendingthem together, or, they may be provided individually.

Co-Additives

The lubricating oil composition of the invention may comprise furtheradditives, different from and additional to (A) and (B). Such additionaladditives may, for example include ashless dispersants, other metaldetergents, anti-wear agents such as zinc dihydrocarbyldithiophosphates, anti-oxidants and demulsifiers. In some cases, anashless dispersant need not be provided.

It may be desirable, although not essential, to prepare one or moreadditive packages or concentrates comprising the additives, wherebyadditives (A) and (B) can be added simultaneously to the base oil toform the lubricating oil composition. Dissolution of the additivepackage(s) into the lubricating oil may be facilitated by solvents andby mixing accompanied with mild heating, but this is not essential. Theadditive package(s) will typically be formulated to contain theadditive(s) in proper amounts to provide the desired concentration,and/or to carry out the intended function in the final formulation whenthe additive package(s) is/are combined with a predetermined amount ofbase lubricant. Thus, additives (A) and (B), in accordance with thepresent invention, may be admixed with small amounts of base oil orother compatible solvents together with other desirable additives toform additive packages containing active ingredients in an amount, basedon the additive package, of, for example, from 2.5 to 90, preferablyfrom 5 to 75, most preferably from 8 to 60, mass % of additives in theappropriate proportions, the remainder being base oil.

The final formulations as a trunk piston engine oil may typicallycontain 30, preferably 10 to 28, more preferably 12 to 24, mass % of theadditive package(s), the remainder being base oil. The trunk pistonengine oil has a compositional TBN (using ASTM D2896) of 20 to 60, suchas, 30 to 55. For example, it may be 40 to 55 or 35 to 50. When the TBNis high, for example 45-55, the concentration of (A) may be high, suchas up to 80 mmol/kg. When the TBN is lower, for example 30 to below 45,the concentration of (A) may be low, such as up to 70 mmol/kg.

EXAMPLES

The present invention is illustrated by but in no way limited to thefollowing examples.

Components

The following components were used:

-   Component (A): one or more calcium alkyl salicylate detergents    having basicity indices of 3-6-   Component (B): a mixed 2- and 4-(linear C16 alkyl)benzenol (2:1)-   Base oil I: solvent-extracted API Group I base oil-   HFO: a heavy fuel oil (ISO-F-RMK 380)

Lubricants

Selections of the above components were blended to give a range of trunkpiston marine engine lubricants. Some of the lubricants are examples ofthe invention; others are reference examples for comparison purposes.The compositions of the lubricants tested when each contained HFO areshown in the tables below under the “Results” heading.

Testing Light Scattering

Test lubricants were evaluated for asphaltene dispersancy using lightscattering according to the Focused Beam Reflectance Method (“FBRM”),which predicts asphaltene agglomeration and hence ‘black sludge’formation.

The FBRM test method was disclosed at the 7^(th) International Symposiumon Marine Engineering, Tokyo, 24-28 Oct. 2005, and was published in ‘TheBenefits of Salicylate Detergents in TPEO Applications with a Variety ofBase Stocks’, in the Conference Proceedings. Further details weredisclosed at the CIMAC Congress, Vienna, 21-24 May 2007 and published in“Meeting the Challenge of New Base Fluids for the Lubrication of MediumSpeed Marine Engines—An Additive Approach” in the Congress Proceedings.In the latter paper it is disclosed that by using the FBRM method it ispossible to obtain quantitative results for asphaltene dispersancy thatpredict performance for lubricant systems based on base stockscontaining greater than or less than 90% saturates, and greater than orless than 0.03% sulphur. The predictions of relative performanceobtained from FBRM were confirmed by engine tests in marine dieselengines.

The FBRM probe contains fibre optic cables through which laser lighttravels to reach the probe tip. At the tip, an optic focuses the laserlight to a small spot. The optic is rotated so that the focussed beamscans a circular path between the window of the probe and the sample. Asparticles flow past the window, they intersect the scanning path, givingbackscattered light from the individual particles.

The scanning laser beam travels much faster than the particles; thismeans that the particles are effectively stationary. As the focussedbeam reaches one edge of the particle the amount of backscattered lightincreases; the amount will decrease when the focussed beam reaches theother edge of the particle.

The instrument measures the time of the increased backscatter. The timeperiod of backscatter from one particle is multiplied by the scan speedand the result is a distance or chord length. A chord length is astraight line between any two points on the edge of a particle. This isrepresented as a chord length distribution, a graph of numbers of chordlengths (particles) measured as a function of the chord lengthdimensions in microns. As the measurements are performed in real time,the statistics of a distribution can be calculated and tracked. FBRMtypically measures tens of thousands of chords per second, resulting ina robust number-by-chord length distribution. The method gives anabsolute measure of the particle size distribution of the asphalteneparticles.

The Focused beam Reflectance Probe (FBRM), model Lasentec D600L, wassupplied by Mettler Toledo, Leicester, UK. The instrument was used in aconfiguration to give a particle size resolution of 1 μm to 1 mm. Datafrom FBRM can be presented in several ways. Studies have suggested thatthe average counts per second can be used as a quantitativedetermination of asphaltene dispersancy. This value is a function ofboth the average size and level of agglomerate. In this application, theaverage count rate (over the entire size range) was monitored using ameasurement time of 1 second per sample.

The test lubricant formulations were heated to 60° C. and stirred at 400rpm; when the temperature reached 60° C. the FBRM probe was insertedinto the sample and measurements made for 15 minutes. An aliquot ofheavy fuel oil (10% w/w) was introduced into the lubricant formulationunder stirring using a four blade stirrer (at 400 rpm). A value for theaverage counts per second was taken when the count rate had reached anequilibrium value (typically overnight).

Results Light Scattering

The results of the FBRM tests are summarized in TABLES 1, 2 and 3 below,where lower particle count indicates better performance.

Comparative examples are designated “Ref” and examples of the inventiondesignated by a number alone.

TABLE 1 Soap Phenol Ex (mmol/kg) (mass %) Particle Counts Ref 1 80 —15.78 Ref 2 80 1.5 13.58 Ref 3 80 3.0 14.83 Ref 4 70 — 37.68 1 70 1.512.25 2 70 3.0 11.96 Ref 5 60 — 136.96 3 60 1.5 15.31 4 60 3.0 12.4

Ref 1, Ref 2 and Ref 3 show that, at high soap levels, the presence orabsence of the phenol has little effect on performance. At lower soaplevels (Ref 4, 1, 2; and Ref 5, 3, 4), the absence of phenol gives poorresults, but performance is restored to about those at 80 mmol/kg (i.e.Ref 1, Ref 2 and Ref 3) when phenol is present.

TABLE 2 Soap Phenol Ex (mmol/kg) (mass %) Particle Counts Ref 6 80 —18.82 Ref 7 70 — 22.23 Ref 8 60 — 77.16 5 60 0.25 47.42 6 60 0.5 43.38 760 1.0 34.48

Ref 6, Ref 7, Ref 8 show that, in the absence of phenol, performancedeteriorates as soap level decreases. 5, 6, 7 show that, at a low soaplevel of 60 mmol/kg, performance is improved by progressive additions ofphenol.

TABLE 3 Soap Phenol Ex (mmol/kg) (mass %) Particle Counts Ref 9  80 —517 Ref 10 70 — 1675 Ref 11 60 — 3916 8 60 0.25 3043 9 60 0.5 1926 10 60 1.0 1896

These results are obtained using a higher asphaltene content heavy fueloil, which is accordingly more difficult to treat.

The same trend as in Table 2 is shown, but less exaggerated. Ref 9, Ref10, Ref 11 show that, in the absence of phenol, performance deteriorateswith decreasing soap level. 8, 9 and 10 show that, at a low soap levelof 60 mmol/kg, performance is partly restored by progressive additionsof phenol.

1. A trunk piston marine engine lubricating oil composition having a TBNin the range of 20 to 60 mg KOH/g, which composition comprises or ismade by admixing an oil of lubricating viscosity, in a major amount,containing 50 mass % or more of a Group 1 basestock, and, in respectiveminor amounts: (A) an overbased calcium alkyl salicylate detergentproviding 40 to 90 mmol of calcium alkyl salicylate per kg of thecomposition, as determined by titration; and (B) 0.1 to 10 mass % activeingredient, based on the mass of the composition, of an oil-solublelinear (straight chain) alkyl-substituted phenol.
 2. The composition asclaimed in claim 1 wherein (A) provides 50 to 80 mmol of calcium alkylsalicylate per kg of the composition.
 3. The composition as claimed inclaim 1 wherein the alkyl substituted phenol of (B) is monosubstitutedwith a linear alkyl group having 9 to 30 carbon atoms.
 4. Thecomposition as claimed in claim 1 wherein (B) is an alkylbenzenol. 5.The composition as claimed in claim 3 wherein (B) is an alkylbenzenol.6. The composition as claimed in claim 4 wherein alkyl-substitution inthe benzenol is in the 2-position or in the 4-position.
 7. Thecomposition as claimed in claim 5 wherein alkyl-substitution in thebenzenol is in the 2-position or in the 4-position.
 8. The compositionas claimed in claim 1 wherein (B) is present in the range of 0.1 to lessthan 0.5 mass % of the mass of the composition.
 9. The composition asclaimed in claim 1 wherein (B) is present in the range of 0.2 to 10 mass% of the mass of the composition.
 10. The composition as claimed inclaim 1 wherein (A) is C₉ to C₃₀ alkyl-substituted.
 11. The compositionas claimed in claim 1 having a TBN in the range of 40 to 55 mg KOH/g.12. The composition as claimed in claim 11 having a TBN in the range of35 to 50 mg KOH/g.
 13. The composition as claimed in claim 1 having aTBN of 45 to 55 mg KOH/g, wherein (A) provides up to 80 mmol of calciumalkyl salicylate per kg of the composition.
 14. The composition asclaimed in claim 1 having a TBN from 30 to less than 45 mg KOH/g,wherein (A) provides up to 70 mmol of calcium alkyl salicylate per kg ofthe composition.
 15. The composition as claimed in claim 1 having aheavy fuel oil content.
 16. A method of operating a trunk pistonmedium-speed compression-ignited marine engine comprising (i) fuelingthe engine with a heavy fuel oil; and (ii) lubricating the crankcase ofthe engine with a composition as defined in claim
 1. 17. A method ofdispersing asphaltenes in a trunk piston marine lubricating oilcomposition during its lubrication of surfaces of the combustion chamberof a medium-speed compression-ignited marine engine and operation of theengine, which method comprises (i) providing a composition as defined inclaim 1; (ii) providing the composition in the combustion chamber; (iii)providing heavy fuel oil in the combustion chamber; and (iv) combustingthe heavy fuel oil in the combustion chamber.